1. Field of the Invention
Aspects of the present invention relate to an electrode assembly, and to a secondary battery including the same, and more particularly, to a secondary battery that protects an electrode assembly, and has improved safety and quality.
2. Description of the Related Art
A secondary battery can be repeatedly charged and discharged. Therefore, a secondary battery is more economical than a disposable battery. Further, as a secondary battery has high capacity in a small size, it is widely used to power portable electronic devices, such as a mobile phone, a notebook computer, a camcorder, a digital camera, and the like. Furthermore, as a secondary battery has a large capacity, it is used for high-power products, such as a hybrid vehicle, an electric tool, and the like.
Examples of a secondary battery include a nickel cadmium battery, a nickel metal hydride battery, a nickel zinc battery, a lithium ion secondary battery, a lithium polymer secondary battery, and the like. Among these batteries, lithium ion secondary batteries are widely used, because they can be small in size, have high capacities, high operating voltages, and high energy densities per unit weight.
A lithium ion secondary battery is made by disposing an electrode assembly and an electrolyte in a cell case, and then sealing the cell case. A lithium secondary battery can be classified as a can-type, or a pouch-type, depending on the configuration of the cell case. A can-type can be further classified as a cylinder-type or a prismatic-type.
A cylinder-type secondary battery is made by disposing an electrode assembly and an electrolyte in a cylindrical can, and then sealing the can with a cap assembly. In the electrode assembly, a positive electrode plate, a negative electrode plate, and a separator are stacked together, and wound.
First and second electrode tabs are connected to the positive electrode plate and the negative electrode plate. The first electrode tab extends toward the cap assembly, and the second electrode tab is drawn downward in the direction of the can. The first electrode tab is electrically connected to the cap assembly, and the second electrode tab is electrically connected to the can.
Before the electrode assembly is disposed in the can, the second electrode tab is bent toward a central portion of the electrode assembly, and welded to the can. If the second electrode tab is not bent at a predetermined position, the electrode assembly is pressed by the second electrode tab, and thus, may be damaged. On the contrary, if the second electrode tab is bent, so as to be excessively spaced apart from the electrode assembly, the electrode assembly is excessively spaced apart from the bottom of the can.
Thus, the electrode assembly may easily move up and down, and capacity may be reduced. If the electrode assembly moves, the second electrode tab is deformed. Thus, the electrode assembly may be damaged, and the second electrode tab may become detached from the can.